How to ensure efficient and stable DC current for green hydrogen
The cell also includes a separator (not shown in this diagram) to prevent the hydrogen and oxygen produced at the electrodes from mixing. The process requires high levels of DC. Under ideal conditions with no energy loss, a minimum of 32.9 kilowatt hours (kWh) of electrical energy is required to electrolyze
The most established electrolyzers are AEL electrolyzers, which use an alkaline solution such as potassium hydroxide between the metal electrodes. They are less efficient than the other types of electrolyzers. PEM electrolyzers use a solid polymer electrolyte enhanced with precious metal catalysts. They are characterized by higher efficiency, faster response times, and compact designs. Solid oxide electrolyzer cells (SOECs) use a solid ceramic material as the electrolyte. They can be highly efficient, but they require high operating temperatures. Their response times are slower than the PEM electrolyzers.
A comparison of the characteristics of the three techniques is shown in Figure 2. Green hydrogen generation currently costs more to produce than hydrogen from fossil fuels. This can be reversed by improving the efficiency of the discrete components, including the electrolyzers and power systems, and scaling up the conversion plants. Power system configurations for grid and green power sources Currently, most hydrogen-generating plants are operating off the power grid. The power source for an electrolyzer is an AC to DC rectifier fed from a line transformer.
enough water molecules to produce 1 kilogram (kg) of
hydrogen. This will vary depending on the efficiency of the electrolysis process being used. Three different processes are currently in use: alkaline electrolysis (AEL), proton exchange membrane (PEM), and solid oxide electrolysis.
Figure 2: A comparison of the characteristics of the AEL, PEM, and SOEC processes highlights the improving efficiencies of the newer electrolyzers. (Image source: Infineon Technologies)
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